Do you have a scripture reference for that? I've looked, but I can't remember where it is. Anyhow, the only sin greater than the rest is blasphemy of the Holy Spirit, which essentially Ciaphas did when he sent the Messiah to Pilate to be crucified. Aside from that, there is actually a "both/and" explanation for whether sins are ranked or not. The word most commonly used in the New Testament greek for "sin" literally means to miss the target. If this is imagined as an archery target and the target is a Christ-like life, then we can be off by a little or clear on the other side of the forest.
John 19:11 "Jesus answered, "You would have no power over me if it were not given to you from above. Therefore the one who handed me over to you is guilty of a greater sin."
For you reverend,
Mark 3:28-29 "I tell you the thruth, all the sins and blasphemeis of men will be forgiven them. but whoever blashemies agaisnst he Holy Spirit will never be forgiven; he is guilty of an eternal sin."
I am not sure, but I think am pretty certain that giving the Son of God over to die is pretty close, but even that isn't clear. There is another scripture that I cannot find at the moment. Today is my wife and I's 5th anniversary and must hurry.